Our overall goal is to clarify the influence of function on the growth and ultimate morphology of the head. The mechanical environment influences skull growth at every level from individual cells to gross structure. Although usually neglected, soft tissues such as muscles, ligaments and cartilages play a critical role in cranial mechanics and growth. This proposal focuses on two ways in which soft tissue mechanics may direct the growth of skull bones, using the pig as a model. First, the osteogenic activity of the periosteum is linked to its blood supply, which originates from muscles and ligaments. We hypothesize that the deformation of these soft tissues during function can modify periosteal perfusion. In Specific Aim 1, new methodology will be employed to map the three-dimensional deformation of muscles and ligaments during awake mastication and to test whether buccinator contraction places significant pressure on the alveolar periosteum. Specific Aim 2 addresses the periosteal vascular system directly with both immunocytochemical assays of cellular activity and in vivo measures of blood flow. These studies will provide evidence for or against a causal linkage between soft tissue behavior and periosteal perfusion. The second way in which soft tissues may direct skull growth involves the nasal septum. Despite being an unmineralized cartilage, the septum has been considered an important mechanical support of the face. Moreover, forces generated by septal growth are claimed to separate the sutures between facial bones, causing compensatory growth. These assertions have never been tested directly. In Specific Aim 3 a novel indwelling transducer will be used to reveal the mechanical loading pattern of the septum and to investigate the timing of its growth in relation to that of facial sutures. Specific Aim 4 will test the mechanical plausibility of the hypothesis that the septum controls facial growth by comparing the viscoelastic stiffness of the cartilaginous septum to the resistance of the facial sutures. Taken together, these studies will develop new techniques for monitoring soft tissue function, provide fundamental new information about the mechanical behavior of the head, and test hypotheses about how soft tissues influence skull growth. [unreadable] [unreadable]